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Abstract:

A system and method of ultrasound imaging includes a beamformer including
a plurality of channels, a two-dimensional transducer array including a
plurality of elements, and a plurality of signal pathways linking the
plurality of elements to the plurality of channels. The system and method
also include a plurality of switches positioned along the plurality of
signal pathways. The plurality of switches being configured to actively
connect a subset of the plurality of elements to the plurality of
channels in order to form a receive aperture. The plurality of switches
are further configured to control an aspect ratio of the receive aperture
by changing which of the plurality of elements are actively connected to
the plurality of channels.

Claims:

1. An ultrasound imaging system comprising: a beamformer including a
plurality of channels; a two-dimensional transducer array comprising a
plurality of elements, the plurality of elements exceeding the plurality
of channels; a plurality of signal pathways, each signal pathway linking
one of the plurality of elements to one of the plurality of channels; and
a plurality of switches positioned along the plurality of signal
pathways, the plurality of switches configured to actively connect a
subset of the plurality of elements to the plurality of channels in order
to form a receive aperture, wherein the plurality of switches are further
configured to control an aspect ratio of the receive aperture by changing
which of the plurality of elements are actively connected to the
plurality of channels.

2. The ultrasound imaging system of claim 1, wherein the plurality of
signal pathways are configured to establish electrical associations
between the plurality of elements and the plurality of channels in a
two-dimensional pattern.

3. The ultrasound imaging system of claim 2, wherein the two-dimensional
pattern is configured to enable the receive aperture to translate across
the two-dimensional array in both the azimuth direction and the elevation
direction while utilizing all of the plurality of channels.

4. The ultrasound imaging system of claim 2, wherein the two-dimensional
pattern comprises a plurality of sub-patterns, each of the plurality of
sub-patterns comprising a fixed arrangement of channel assignments.

6. The ultrasound imaging system of claim 5, wherein the N unique
sub-patterns are arranged in a grid of columns and rows.

7. The ultrasound imaging system of claim 6, wherein the N unique
sub-patterns are arranged in a fixed order within each of the rows.

8. The ultrasound imaging system of claim 7, wherein the N unique
sub-patterns are arranged with an offset of N/2 between adjacent rows.

9. The ultrasound imaging system of claim 6, wherein the N unique
sub-patterns are arranged in a fixed order within each of the columns.

10. The ultrasound imaging system of claim 9, wherein the N unique
sub-patterns are arranged with an offset of N/2 between adjacent columns.

11. An ultrasound imaging system with a configurable receive aperture
comprising: a beamformer including a plurality of channels; a
two-dimensional transducer array comprising a plurality of elements, the
plurality of elements exceeding the plurality of channels, each of the
elements electrically associated with one of the channels in a
two-dimensional pattern, the two-dimensional pattern comprising a first
sub-pattern of two-dimensional channel assignments and a second
sub-pattern of two-dimensional channel assignments; and a plurality of
switches configured to control which the plurality of elements are
actively connected to the plurality of channels; wherein the plurality of
switches and the two-dimensional pattern are adapted to enable a first
subset of the plurality of elements to be actively connected to the
plurality of channels in order to form a first receive aperture with a
first aspect ratio; wherein the plurality of switches and the
two-dimensional pattern are further adapted to enable a second subset of
the plurality of elements to be actively connected in order to form a
second receive aperture with a second aspect ratio.

12. The ultrasound imaging system of claim 11, wherein the first
sub-pattern and the second sub-pattern are arranged in an alternating
manner within the two-dimensional pattern.

13. The ultrasound imaging system of claim 11, wherein the
two-dimensional pattern further comprises a third sub-pattern and a
fourth sub-pattern.

14. The ultrasound imaging system of claim 13, wherein the first
sub-pattern, the second sub-pattern, the third sub-pattern, and the
fourth sub-pattern are positioned within the two-dimensional pattern in
an alternating manner.

15. The ultrasound imaging system of claim 14, wherein the sub-patterns
are arranged in a plurality of rows and columns within the
two-dimensional pattern.

16. The ultrasound imaging system of claim 15, wherein the sub-patterns
are arranged in a fixed order in each of the plurality of rows.

17. The ultrasound imaging system of claim 15, wherein the sub-patterns
are arranged in a fixed order in each of the plurality of columns.

18. The ultrasound imaging system of claim 11, wherein the plurality of
switches and the two-dimensional pattern are configured to enable the
first receive aperture to translate across the two-dimensional array in
both an elevation direction and in an azimuth direction while using all
of the plurality of channels.

19. A method of ultrasound imaging comprising: grouping elements of a
two-dimensional transducer array into a plurality of sub-apertures;
assigning each of the plurality of sub-apertures to a channel from a
beamformer in a two-dimensional pattern; connecting a first subset of the
plurality of sub-apertures to the channels from the beamformer according
to the channel assignments in the two-dimensional pattern to form a first
receive aperture with a first aspect ratio; and connecting a second
subset of the plurality of sub-apertures to the channels from the
beamformer according to the channel assignments in the two-dimensional
pattern to form a second receive aperture with a second aspect ratio.

20. The method of claim 20, wherein assigning each of the sub-apertures
to a channel from the beamformer comprises assigning each of the
sub-apertures to a channel in a pattern comprising a plurality of
sub-patterns.

Description:

FIELD OF THE INVENTION

[0001] This disclosure relates generally to ultrasound imaging and
specifically to a two-dimensional ultrasound transducer array with a
configurable receive aperture.

BACKGROUND OF THE INVENTION

[0002] A conventional ultrasound imaging system comprises an array of
ultrasonic transducer elements for transmitting an ultrasound beam and
receiving a reflected beam from the object being studied. By selecting
the time delay (or phase) and amplitude of the applied voltages, the
individual elements can be controlled to produce ultrasonic waves which
combine to form a net ultrasonic wave that travels along a preferred
vector location and direction and is focused at a selected point along
the beam. Multiple firings may be used to acquire data representing the
same anatomical information. The beamforming parameters of each of the
firings may be varied to provide a change in maximum focus or otherwise
change the content of the received data for each firing, e.g., by
transmitting successive beams along the same scan line with the focal
point of each beam being shifted relative to the focal point of the
previous beam. By changing the time delay and amplitude of the applied
voltages, the beam with its focal point can be moved in a plane to scan
the object.

[0003] The same principles apply when the transducer array is employed to
receive the reflected sound energy. The voltages produced at the
receiving elements are summed so that the net signal is indicative of the
ultrasound reflected from points in the object. As with the transmission
mode, this focused reception of the ultrasonic energy is achieved by
imparting a separate time delay (and/or phase shift) and gain to the
signal from each receiving element. The receive delays may be modified
during reception to dynamically increase the focal depth as echoes are
received from progressively deeper points along a line within the
transmit beam.

[0004] Recently, many conventional ultrasound imaging systems have
included a two-dimensional transducer array (hereinafter a 2D transducer
array). The 2D transducer array typically comprises a number of
transducer elements arranged in a grid. By controlling the timing and
amplitude of the elements in the 2D transducer array, it is possible to
steer and translate the transmitted ultrasound beam in both an azimuth
direction and in an elevation direction. The use of a 2D transducer array
allows the ultrasound transducer or probe to have greater flexibility and
it enables greater accuracy in the acquisition of volumetric data.

[0005] However, for some ultrasound systems and probes, the number of
transducer elements exceeds the number of channels in the console
beamformer electronics or the number of channels supported by the console
interface. For example, a 2D transducer array used for 3D and 4D imaging
may require a very high number of elements, roughly the square of the
number of elements needed for a 1D array used for 2D imaging. For
example, a linear array which would required 128 to 192 elements for 2D
imaging would need approximately 8,000 to 10,000 elements for 3D and 4D
imaging. In cases like this, one or more probe beamforming and/or
switching circuits may be used to dynamically couple the available
channels to different subsets of transducer elements during different
portions of the image formation process. Even if a probe beamforming
circuit, also known as a sub-aperture processor (SAP), is used to combine
10 or more elements for each console beamformer channel, there may still
not be enough console beamformer channels to utilize all of the elements
in the 20 transducer array.

[0006] Additionally, while scanning a single slice, such as for a 2D
display, it is often desirable to optimize the resolution within the
slice. One way to optimize the resolution is to use a receive aperture
that has its widest extent in the scanning dimension. For example, when
scanning in the azimuth direction, it may be desirable to have a receive
aperture that is widest in the azimuth direction. Likewise, when scanning
in the elevation direction, it may be desirable to have a receive
aperture that is widest in the elevation direction. Additionally, when
scanning a volume to render as a 3D or 4D image, it may be desirable to
optimize the resolution for more uniformity in both scanning dimensions
by using an aperture that is shaped more like a square. For these and
other reason, there is a need for an easily configurable ultrasound
imaging system with the flexibility to optimize the shape of the receive
aperture of a 2D transducer array based on the type of image that is
desired.

BRIEF DESCRIPTION OF THE INVENTION

[0007] The above-mentioned shortcomings, disadvantages and problems are
addressed herein which will be understood by reading and understanding
the following specification.

[0008] In an embodiment, an ultrasound imaging system includes a
beamformer including a plurality of channels. The ultrasound imaging
system includes a two-dimensional transducer array including a plurality
of elements, the plurality of elements exceeding the plurality of
channels. The ultrasound imaging system includes a plurality of signal
pathways, each signal pathway linking one of the plurality of elements to
one of the plurality of channels. The ultrasound imaging system also
includes a plurality of switches positioned along the plurality of signal
pathways. The plurality of switches are configured to actively connect a
subset of the plurality of elements to the plurality of channels in order
to form a receive aperture. The plurality of switches are further
configured to control an aspect ratio of the receive aperture by changing
which of the plurality of elements are actively connected to the
plurality of channels.

[0009] In another embodiment, an ultrasound imaging system with a
configurable receive aperture includes a beamformer including a plurality
of channels. The ultrasound imaging system includes a two-dimensional
transducer array comprising a plurality of elements, the plurality of
elements exceeding the plurality of channels. Each of the elements is
electrically associated with one of the channels in a two-dimensional
pattern. The two-dimensional pattern includes a first sub-pattern of
two-dimensional channel assignments and a second sub-pattern of
two-dimensional channel assignments. The ultrasound imaging system
includes a plurality of switches configured to control which of the
plurality of elements are actively connected to the plurality of
channels. The plurality of switches and the two-dimensional pattern are
adapted to enable a first subset of the plurality of elements to be
actively connected to the plurality of channels in order to form a first
receive aperture with a first aspect ratio. The plurality of switches and
the two-dimensional pattern are further adapted to enable a second subset
of the plurality of elements to be actively connected in order to form a
second receive aperture with a second aspect ratio.

[0010] In another embodiment, a method of ultrasound imaging includes
grouping elements of a two-dimensional transducer array into a plurality
of sub-apertures and assigning each of the plurality of sub-apertures to
a channel from the beamformer in a two-dimensional pattern. The method
includes connecting a first subset of the plurality of sub-apertures to
the channels from the beamformer according to the channel assignments in
the two-dimensional pattern to form a first receive aperture with a first
aspect ratio. The method also includes connecting a second subset of the
plurality of sub-apertures to the channels from the beamformer according
to the channel assignments in the two-dimensional pattern to form a
second receive aperture with a second aspect ratio.

[0011] Various other features, objects, and advantages of the invention
will be made apparent to those skilled in the art from the accompanying
drawings and detailed description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a schematic diagram of an ultrasound imaging system in
accordance with an embodiment;

[0013]FIG. 2 is a schematic diagram of an ultrasound imaging system in
accordance with an embodiment;

[0014]FIG. 3 is a schematic diagram of an ultrasound imaging system in
accordance with an embodiment;

[0015]FIG. 4 is a schematic representation of a two-dimensional
transducer array in accordance with an embodiment;

[0016]FIG. 5 is a schematic representation of a two-dimensional
transducer array in accordance with an embodiment;

[0017]FIG. 6 is a schematic representation of a two-dimensional pattern
showing channel assignments for a two-dimensional transducer array in
accordance with an embodiment;

[0018]FIG. 7 is a schematic representation of four sub-patterns in
accordance with an embodiment;

[0019]FIG. 8 is a schematic representation of signal pathways linking
sub-apertures to channels in accordance with an embodiment; and

[0020]FIG. 9 is a schematic representation of a two-dimensional pattern
in accordance with an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0021] In the following detailed description, reference is made to the
accompanying drawings that form a part hereof, and in which is shown by
way of illustration specific embodiments that may be practiced. These
embodiments are described in sufficient detail to enable those skilled in
the art to practice the embodiments, and it is to be understood that
other embodiments may be utilized and that logical, mechanical,
electrical and other changes may be made without departing from the scope
of the embodiments. The following detailed description is, therefore, not
to be taken as limiting the scope of the invention.

[0022]FIG. 1 is a schematic diagram of an ultrasound imaging system 100.
The ultrasound imaging system 100 includes a console transmitter 102 that
transmits a signal to a console transmit beamformer 103 which in turn
drives elements 104 within a transducer array 106 to emit pulsed
ultrasonic signals into a structure, such as a patient (not shown). A
probe assembly 105 includes the transducer array 106, the elements 104
and probe/SAP electronics 107. The probe/SAP electronics 107 may be used
to control the switching of the elements 104. The probe/SAP electronics
107 may also be used to group the elements 104 into one or more
sub-apertures. A variety of geometries of transducer arrays may be used.
The pulsed ultrasonic signals are back-scattered from structures in the
body, like blood cells or muscular tissue, to produce echoes that return
to the elements 104. The echoes are converted into electrical signals, or
ultrasound data, by the elements 104 and the electrical signals are
received by a console receiver 108. For purposes of this disclosure, the
term ultrasound data may include data that was acquired and/or processed
by an ultrasound system. The electrical signals representing the received
echoes are passed through a console receive beamformer 110 that outputs
ultrasound data. A user interface 115 may be used to control operation of
the ultrasound imaging system 100, including, to control the input of
patient data, to change a scanning or display parameter, and the like.

[0023] The ultrasound imaging system 100 also includes a processor 116 to
process the ultrasound data and prepare frames of ultrasound information
for display on a display 118. The processor 116 may be adapted to perform
one or more processing operations according to a plurality of selectable
ultrasound modalities on the ultrasound information. The ultrasound
information may be processed in real-time during a scanning session as
the echo signals are received. For the purposes of this disclosure, the
term "real-time" is defined to include a procedure that is performed
without any intentional delay. Additionally or alternatively, the
ultrasound information may be stored temporarily in a buffer (not shown)
during a scanning session and processed in less than real-time in a live
or off-line operation. Some embodiments of the invention may include
multiple processors (not shown) to handle the processing tasks. For
example, a first processor may be utilized to demodulate and decimate the
ultrasound signal while a second processor may be used to further process
the data prior to displaying an image. It should be appreciated that
other embodiments may use a different arrangement of processors.

[0024] Still referring to FIG. 1, the ultrasound imaging system 100 may
continuously acquire ultrasound information at a frame rate of, for
example, 20 Hz to 30 Hz. However, other embodiments may acquire
ultrasound information at a different rate. For example, some embodiments
may acquire ultrasound information at a frame rate of over 100 Hz
depending on the intended application. A memory 120 is included for
storing processed frames of acquired ultrasound information that are not
scheduled to be displayed immediately. In an exemplary embodiment, the
memory 120 is of sufficient capacity to store at least several seconds
worth of frames of ultrasound information. The frames of ultrasound
information are stored in a manner to facilitate retrieval thereof
according to its order or time of acquisition. The memory 120 may
comprise any known data storage medium.

[0025] Optionally, embodiments of the present invention may be implemented
utilizing contrast agents. Contrast imaging generates enhanced images of
anatomical structures and blood flow in a body when using ultrasound
contrast agents including microbubbles. After acquiring ultrasound data
while using a contrast agent, the image analysis includes separating
harmonic and linear components, enhancing the harmonic component and
generating an ultrasound image by utilizing the enhanced harmonic
component. Separation of harmonic components from the received signals is
performed using suitable filters. The use of contrast agents for
ultrasound imaging is well-known by those skilled in the art and will
therefore not be described in further detail.

[0026] In various embodiments of the present invention, ultrasound
information may be processed by other or different mode-related modules
(e.g., B-mode, Color Doppler, power Doppler, M-mode, spectral Doppler
anatomical M-mode, strain, strain rate, and the like) to form 2D or 3D
data sets of image frames and the like. For example, one or more modules
may generate B-mode, color Doppler, power Doppler, M-mode, anatomical
M-mode, strain, strain rate, spectral Doppler image frames and
combinations thereof, and the like. The image frames are stored and
timing information indicating a time at which the image frame was
acquired in memory may be recorded with each image frame. The modules may
include, for example, a scan conversion module to perform scan conversion
operations to convert the image frames from Polar to Cartesian
coordinates. A video processor module may be provided that reads the
image frames from a memory and displays the image frames in real time
while a procedure is being carried out on a patient. A video processor
module may store the image frames in an image memory, from which the
images are read and displayed.

[0027] Referring to FIG. 2, a schematic diagram of an ultrasound imaging
system 122 is shown in accordance with an embodiment. Elements of the
ultrasound imaging system 122 that are the same as elements from the
ultrasound imaging system 100 shown in FIG. 1 will be labeled with common
reference numbers and will not be described in detail. In the ultrasound
imaging system 122, a probe assembly 123 includes a high-voltage
switching assembly 124 connected to the transducer array 106 and the
elements 104. The high-voltage switching assembly 124 allows the probe
assembly 123 to use a common circuit (not shown) for both transmit and
receive functions.

[0028] Referring to FIG. 3, a schematic diagram of an ultrasound imaging
system 130 is shown in accordance with an embodiment. Elements of the
ultrasound imaging system 130 that are the same as elements from the
ultrasound imaging system 100 shown in FIG. 1 and the ultrasound imaging
system 122 shown in FIG. 2 will be labeled with common reference numbers
and will not be described in detail. The ultrasound imaging system 130
includes a probe assembly 132 comprising a probe transmit switching
assembly 134 and a probe receiver 136. According to an embodiment, the
probe transmit switching assembly 134 may be used in place of the console
transmitter 102 to generate an ultrasound transmit signal. It should be
appreciated by those skilled in the art that the probe transmit switching
assembly 134 may perform a beamforming function according to some
embodiments. Additionally the probe receiver 136 may receive and provide
beamforming for the received signal in place of, or in addition to, the
console receive beamformer 110 in other embodiments.

[0029] Referring to FIG. 4, a schematic representation of a
two-dimensional (2D) transducer array is shown in accordance with an
embodiment. The 2D transducer array 150 may be connected to an ultrasound
imaging system such as the ultrasound imaging system 100 shown in FIG. 1.
The 2D ultrasound array comprises a plurality of elements 152. According
to an embodiment, there may be 7680 elements arranged into 160 columns
and 48 rows. The schematic representation of the 2D transducer array
shows all 48 rows, but it includes only a small number of the columns for
clarity. The 48 rows run in an elevation direction and the 160 columns
run in an azimuth direction. For purposes of the figures within this
disclosure, the azimuth direction will be defined to include an
x-direction and the elevation direction will be defined to include a
y-direction.

[0030] Referring to FIG. 5, a schematic representation of a 2D transducer
array is shown in accordance with an embodiment. The 2D transducer array
200 comprises a plurality of elements 202 arranged into 160 columns and
48 rows in a manner similar to the embodiment described with respect to
FIG. 4. However, the elements 202 are further grouped into a plurality of
sub-apertures 204. According to an embodiment, each of the sub-apertures
204 comprises 15 elements arranged in a generally triangular shape. For
example, a first sub-aperture 206 is indicated with stippling, a second
sub-aperture 208 is indicated with //-hatching, a third sub-aperture 210
is indicated by \\-hatching, and a fourth sub-aperture 212 is indicated
by cross-hatching. Only four of the sub-apertures are indicated in FIG.
5. However, it should be appreciated by those skilled in the art that all
of the elements may be arranged into sub-apertures in a manner consistent
with the first sub-aperture 206, the second sub-aperture 208, the third
sub-aperture 210, and the fourth sub-aperture 212. According to an
embodiment, the elements that comprise a sub-aperture may each have a
relative timing or phase offset that enables each sub-aperture to focus
in an independent direction if desired. However, each of the
sub-apertures 204 may be configured to output its signal to a single
beamformer channel in order to minimize the total number of channels
needed for a given number of elements 202. According to an embodiment,
all of the plurality of elements 202 may be arranged into 15-element sub
apertures. For example, the elements 202 of the transducer array 200 may
be arranged into 8 rows of 48 sub apertures. In FIG. 5, only the first
four of the sub-apertures are indicated. It should be appreciated by
those skilled in the art that in other embodiments the transducer
elements may be arranged into sub-apertures that are different from those
depicted in FIG. 5. For example, embodiments may by configured with
sub-aperture processing configured to create sub-apertures with shapes
including a square, a rectangular, or a diamond. It should also be
appreciated that other embodiments may not employ sub-aperture
processing. For embodiments without sub-aperture processing, the each of
the elements may be directly connected to a single beamformer channel.

[0031] Referring to FIG. 6, a schematic representation of a
two-dimensional pattern showing element to channel assignments for a
two-dimensional transducer array is shown according to an embodiment. The
two-dimensional pattern 250 includes a plurality of sub-patterns 252. The
letters A, B, C, and D are used to indicate each of the four unique
sub-patterns in the two-dimensional pattern 250. Each of the sub-patterns
represents a fixed spatial arrangement of channel assignments. For
example, the sub-pattern A represents a fixed spatial arrangement of
channel assignments. According to an embodiment, each of the channel
assignments within the sub-pattern may represent a signal pathway linking
one or more elements to a beamformer channel. Additional description of
the signal pathways will be provided hereinafter.

[0032] Referring to FIG. 7, a schematic representation of multiple
sub-patterns is shown in accordance with an embodiment. A first
sub-pattern A, a second sub-pattern B, a third sub-pattern C, and a
fourth sub-pattern D each represent a pattern of linking transducer array
elements to beamformer channels. The sub-patterns A, B, C, and D may be
used with a transducer array such as the transducer array 200 (shown in
FIG. 3). According to an embodiment, the beamformer 110 (shown in FIG. 1)
may have 256 channels. The transducer array 200 has 7680 elements
arranged into 512 sub-apertures 204 (shown in FIG. 5). According to an
embodiment, each of the sub-apertures 204 is linked to one of the
beamformer channels. Details of the linking between the sub-apertures 204
and the beamformer channels will be discussed in detail hereinafter.

[0033] The first sub-pattern A shows one way that sub-apertures may be
linked to beamformer channels in a two-dimensional pattern. In FIG. 7,
each of the triangular shapes represents a sub-aperture. The numbers 0-63
correspond to the channels to which each of the sub-apertures are linked.
For example, a sub-aperture 258 is linked to channel 0 while a
sub-aperture 260 is linked to channel 44.

[0034] The second sub-pattern B 252 shows a two-dimensional pattern
linking sub-apertures to channels 64 to 127. The third sub-pattern C
shows a fixed two-dimensional pattern linking sub-apertures to channels
128-191. The fourth sub-pattern D shows a fixed two-dimensional pattern
linking sub-apertures to channels 192-255. According to the embodiment
shown in FIG. 7, the sub-apertures are linked to beamformer channels in
ascending order starting at the upper left and rastering through the
subsequent rows. The sub-apertures of other embodiments may be linked to
the beamformer channels in other patterns in accordance with other
embodiments.

[0035] Referring now to FIGS. 6 and 7. FIG. 6 shows the first sub-pattern
A, the second sub-pattern B, the third sub-pattern C, and the fourth
sub-pattern D arranged in a two-dimensional pattern 250. According to an
embodiment, the two-dimensional pattern 250 contains each of the
sub-patterns repeated three times. For example, the first sub-pattern A
is repeated three times in the two-dimensional pattern 250. The first
sub-pattern A is the same in each of the three locations within the
two-dimensional pattern 200. Sub-pattern B, sub-pattern C, and
sub-pattern D are also each repeated three times within the
two-dimensional pattern 250.

[0036] The two-dimensional pattern 250 represents the channel assignments
of all of the elements in a two-dimensional array. Each location within
the two-dimensional pattern 250 corresponds with a portion of a
two-dimensional transducer array. The two-dimensional pattern 250
includes information about the way the elements of the transducer array
are linked to the beamformer channels. Based on the exemplary embodiment
shown in FIGS. 6 and 7, four unique sub-patterns are used to represent
all of the beamformer channels. In order to form a receive aperture using
all of the beamformer channels, it is therefore necessary to use elements
from at least the first sub-pattern A, the second sub-pattern B, the
third sub-pattern C, and the fourth sub-pattern a The sub-patterns 252
are arranged in an alternating manner in the two-dimensional pattern 250.
For the purposes of this disclosure, the term "alternating manner" is
defined to include patterns where each sub-pattern is either adjacent to
the edge of the transducer array or to a different sub-pattern. In other
words, in a two-dimensional pattern where the sub-patterns are arranged
in an alternating manner, each sub-pattern is next to either a
sub-pattern of a different configuration or an edge of the transducer
array. A two-dimensional pattern with the sub-patterns arranged in an
alternating manner would not include two of the same sub-patterns
positioned next to each other.

[0037] Referring to FIG. 6, a first receive aperture 270 is shown. The
first receive aperture 270 is indicated with //-hatching. A second
receive aperture 272 is also shown. The second receive aperture 272 is
indicated with \\-hatching. Elements within two of the sub-patterns are
used in both the first receive aperture 270 and the second receive
aperture 272. The portion of the two-dimensional pattern 250
corresponding to elements used in both the first receive aperture 270 and
the second receive aperture 272 is indicated with cross-hatching.

[0038] Referring to FIG. 8, a schematic representation of signal pathways
linking sub-apertures to channels is shown in accordance with an
embodiment. There are a plurality of signal pathways 290 linking three
sub-apertures to each channel according to an embodiment. For example, a
first signal pathway 300 links channel 0 to sub-aperture 301, a second
signal pathway 302 links channel 0 to sub-aperture 303, and a third
signal pathway 304 links channel 0 to sub-aperture 305. A plurality of
switches 306 is positioned along the plurality of signal pathways 290.
The plurality of switches 306 control which of the sub-aperture are
actively connected to the beamformer channels. For example, according to
an embodiment, only one of sub-aperture 305, sub-aperture 303, and
sub-aperture 301 may be connected to channel 0 at a time. According to
other embodiments, the channels may be linked to individual elements
instead of sub-apertures.

[0039] The plurality of signal pathways 290 and the plurality of switches
306 may be part of an integrated circuit (not shown) in accordance with
an embodiment. The integrated circuit may positioned within the
transducer. Each of the signal pathways 290 represents an electrical
pathway linking a group of elements in a sub-aperture to a beamformer
channel. According to other embodiments, each of the plurality of signal
pathways may connect a single element of the transducer array to a
beamformer channel.

[0040] Referring now to both FIG. 6 and FIG. 8, the sub-patterns 252 are
arranged in a fixed order within all of the columns. For example, from
top to bottom, all of the sub-patterns are arranged in an A-B-C-D order.
In a first column 310, the sub-patterns are arranged A-B-C-D. In a second
column 312, the sub-patterns are arranged C-D-A-B. The sub-patterns in
the second column 312 are in the same order as in the first column, but
there is an offset of 2 between the adjacent columns. In a third column
314, the sub-patterns are again arranged in A-B-C-D. There is also an
offset of 2 between the second column 312 and the third column 314. It
should be understood by those skilled in the art that other embodiments
may use a different number of unique sub-patterns. Additionally, the
two-dimensional pattern may comprise a different arrangement of the
sub-patterns.

[0041] Still referring to FIG. 6 and FIG. 8, the first receive aperture
270 is longer in the elevation direction than in the azimuth direction.
Conversely, the second receive aperture 272 is longer in the azimuth
direction than in the elevation direction. When scanning a single slice
for a two-dimensional display, it is often desirable to optimize the
resolution within the slice by using a receive aperture with its widest
extent in the scanning dimension. By linking channels to elements or
sub-apertures as shown in FIG. 6, it is possible to have two different
receive apertures, each with a different aspect ratio. For example, the
first receive aperture 270 has a first aspect ratio and is configured to
give a higher resolution when scanning in the elevation direction. The
second receive aperture 272 has a second aspect ratio and is configured
to give a higher resolution when scanning in the azimuth direction. It
should be noted that according to an embodiment, it is possible to
utilize all the beamformer channels with both the first receive aperture
270 and the second receive aperture 272. Additional embodiments may be
configured to provide more than two different receive apertures.

[0042] Referring to FIG. 9, the two-dimensional pattern 250 from FIG. 6 is
shown in accordance with an embodiment. Common reference numbers are used
to indicate identical elements. According to an embodiment, the first
receive aperture 270 may be configured to translate across the
two-dimensional array. The sub-patterns of the two-dimensional pattern
250 are organized into three columns. Each of these columns includes four
sub-patterns. The channels assignments for a given channel are in the
same relative position within each of the common sub-patterns. For
purposes of this disclosure, the term "common sub-patterns" is defined to
include two or more sub-patterns with the same channel assignments in the
same relative positions. Common sub-patterns are indicated with the same
letter, such as A, B, C, or D within the figures of this disclosure. For
example, the sub-patterns indicated by reference numbers 360, 362, and
364 are all common sub-patterns.

[0043] Still referring to FIG. 9, since the channel assignments are fixed
within each of the common sub-patterns, it is possible to shift a receive
aperture while utilizing all of the available beamformer channels. The
first receive aperture 270 is indicated with //-hatching. Channels
assigned from sub-pattern A, sub-pattern B, sub-pattern C, and
sub-pattern D are actively connected to elements in the transformer array
in order to form the first receive aperture 270. However, by opening a
first set of switches connecting channels 386, indicated by stippling, on
the left-hand side of the first receive aperture 270 and closing a second
set of switches connecting channels 388, also indicated by stippling, to
the right of the first receive aperture 270, it is possible translate the
first receive aperture 270 to the right. Note that the sub-patterns used
in the second column 312 are the same as the sub-patterns in the third
column 314. As described previously, the channel assignments are the same
within each of the common sub-patterns. Since the channel assignments are
the same for all common sub-patterns, by turning off an element or
elements associated with a given channel in one sub-pattern and turning
on an element of element associated with the same channel in a common
sub-pattern that is adjacent to the current receive aperture, it is
possible to cause the receive aperture to translate in position.
Additionally, since the same channels are used in both positions, it is
possible use all of the beamformer channels for the first receive
aperture 270 in both its initial position and in its translated position.
In other words, if a first set of channels, such as channels 386, are
disconnected from the receive aperture 270 while a second set of
channels, such as channels 388 are connected, all of the same channels
may be utilized in the newly-shifted receive aperture. An important
aspect of this embodiment is that by arranging the sub-patterns 252 in
the two-dimensional pattern 250, it is possible to translated the first
receive aperture 270 in the azimuth direction while still utilizing all
of the beamformer channels. It should be appreciated by those skilled in
the art that it would be possible to translate the second receive
aperture 272 (shown in FIG. 4) in both the azimuth direction and the
elevation direction for the same reasons described hereinabove with
respect to the first sub-aperture 270. It should be appreciated by those
skilled in the art that while a specific two-dimensional pattern 250 was
described in detail other embodiments may use a different two-dimensional
pattern with either a different number or arrangement of common
sub-patterns.

[0044] This written description uses examples to disclose the invention,
including the best mode, and also to enable any person skilled in the art
to practice the invention, including making and using any devices or
systems and performing any incorporated methods. The patentable scope of
the invention is defined by the claims, and may include other examples
that occur to those skilled in the art. Such other examples are intended
to be within the scope of the claims if they have structural elements
that do not differ from the literal language of the claims, or if they
include equivalent structural elements with insubstantial differences
from the literal language of the claims.